Larvicidal activities of Bacillus thuringiensis (Bt) on larvae of Culex quinquefasciatus in lymphatic filariasis vector control in Lokossa district in south-western Republic of Benin, West Africa

Background: Mosquito control programs are now threatened by the selection of mosquito populations resistant to the chemical insecticides. Thus, alternative vector control methods are necessary. Objective: This study was aimed at investigating on the larvicidal activities of Bacillus thuringiensis (Bt) on larvae of Culex quinquefasciatus in lymphatic filariasis vector control in Lokossa district in Mono department in south-western Benin, West Africa. Material and Methods: Larvae of Culex quinquefasciatus Say mosquitoes were collected from breeding sites using the dipping method from September to November 2024 during the small rainy season in Lokossa district. A batch of 25 larvae of fourth instar were exposed to a mixture of Bacillus thuringiensis with distilled water saturated with oxygen containing in each of five glass jars or test cups of same dimensions with different concentrations of 1mg/l, 2mg/l, 3mg/l, 4mg/l and 5mg/l and one control jar for each serial concentrations containing no trace of Bacillus thuringiensis. Larval mortality was recorded after 24 hours, 48 hours and 72hours exposure. Results: The results showed that Bacillus thuringiensis had acted by poisoning the larvae of four instars which could not breathe and pupate. Conclusion: The use of Bacillus thuringiensis disallows mosquito larvae to acquire tolerance.